1. Field of Invention
The present invention relates to a technique of surface ornamentation. More particularly, the present invention relates to a surface ornamentation method for composite material.
2. Description of Related Art
Precision electronic components in mobile electronic devices have to be well protected by plastic shells made by strong and light materials to facilitate the needs of mobile devices. Composite material, plastics matrix material mixed with and containing reinforcing fibers of short and long length, is one of the conventional fiber reinforced material usually used for producing plastic shells.
The process of using composite materials to produce plastic shells for mobile electronic products includes the following steps. A plastic material and fibers are mixed together to form a sheet of composite material. The composite material is then cut to the proper size. Next, the sheet of the composite material is placed in a mold to perform a mold-pressing process at high temperature and high pressure to obtain a material with desired three-dimensional shape. Finally, the mold is opened and the product is taken out.
An organic solvent is required to uniformly mix plastic material and fibers. If plastic material and fibers are not uniformly mixed, bubbles which cause surface defect can be easily formed in the mold-pressing step. Before paint is sprayed onto the surface of the shell product, the surface has to be polished in order to obtain a decent product, or the thickness of the paint can be increased to minimize the effect of defects on the surface.
However, the polishing process decreases product throughput and increases product price. Moreover, occupational injury is possible if powders generated in the polishing process are inhaled by operators. Besides, the increase of paint thickness on the shell surface cannot totally resolve the surface defect problem, and spraying thick paint also leads to low product yield.